Remote control apparatus for radioreceivers



A. A. THOMAS REMOTE CONTROL APPARATUS FOR RADIORECEIVERS 9 Sheets-Shet 1 Filed Marbh 24, 1930 INVENTOR Aug. 13, 1935. A. A. THOMAS REMOTELCONTROL APPARATUS FOR RADIORECEIVERS 9 Sheets-Sheet 2 Filed March 24, 1930 1935. A. A. THOMAS 2,010,904

REMOTE CONTROL APPARATUS FOR RADIORECEIVERS Filed March 24, 1930 9 Sheets-Sheet 5 /07 I NVENTOR Aug. 13,- 1935. A. A. THOMAS 2,010,904

EMOTE CONTROL APPARATUS FOR RADIORECEIVERS Filed March 24, 1930 9 Sheets-Sheet 4 l 0 //7 /2/ as v INVENTOR Aug. 13, 1935. A.- A. THOMAS 2,010,904

REMOTE CONTROL APPARATUS FOR RADIORECEIVERS Filed March 24, 1930 9 Sheets-Sheet INVEN'I'OR Aug. 13, 1935. A. A. THOMAS 4 REMOTE CONTROL APPARATUS FOR RADIORECEIVERS 9 Sheet-Sheet 7 Filed March 24, 1930 INVENTOR mh/ww Aug. 13, 1935.

A. A. THOMAS 2,010,904

REMOTE CONTROL APPARATUS FOR RADIORECEIVERS Filed March 24, 1930 9 sheets-sheet 8 INVENTOR Patented Aug 13, 1935 UNITED STATES PATENT OFFICE REMOTE CONTROL APPARATUS FOR RADIORECEIVERS Adolph A. Thomas, New York, N. Y.

Application March 24, 1930, Serial No. 438,312

20 Claims. (01. 172-239) My invention relates to the art of receiving radio broadcasts and its object is to provide novel means for controlling the operation of a radio receiver at a distance. The remote tuning system of my invention is characterized by simplicity of structure for tuning in any station without the need-of individual controlling switches in the receiver. I require only one controlling switch to stop the tuning shaft in selected position, and this tuning switch, as I may call it, is movably mounted in such a way that the moment of its closing (or opening) is predetermined by the strength of current passing through the coil of an electromagnet operating device. In a remote control box is a rheostat or equivalent means for regulating the current strength in the switchcontrolling coil by a movable finger piece or a set of push buttons. The remote control box is operatively connected to the receiver by an electric cable which contains only a few wires of low voltage.

In one form of my invention, the tuning switch comprises a contact movable with the tuning shaft and a second contact movable to a selected position by an electromagnetic coil. The position of the second contact, which moves independently of the tuning shaft, is controlled by regulating the curent strength in the coil, as previously. mentioned. In other words, the position of the second contact in relation to'the first contact determines the position in whichthe tuning shaft stops. When the two contacts meet, they energize a relay to open the circuit of the electric motor that drives the tuning shaft. The contacts of the tuning switch may be mounted for rotary or rectilinear movement.

It is not necessarythat the two contacts of the tuning switch shall be mounted on separately movable supports, for both contacts can be arranged on the same movable member as a unitary switch either normally open or closed.

In that case, there is a separate member movable by the electromagnetic coil to a predetermined position in accordance with the-strength of the energizing current. When this member encounters the movable switch, the latter is closed (or opened, as the case may be) to break the motor circuit and stop the tuning shaft in position for the selected station.

The electromagnetic device for controlling the operation of the tuning switch may be a solenoid with a movable core and a fixed coil, or it may comprise a coil pivoted in a magnetic field. In either case, the final position of the movable part is controlled .by the strength of current passing through thecoil, and it is the position of this movable part that determines the position in which the tuning shaft comes to rest. This electromagnetic device is so calibrated that an energizing current of given value causes a certain station to be tuned in, and an indicator on the remote control box enables the operator to select the station he wants. The position of the indicator corresponds to the strength of current passing through the switch-controlling coil in the erator releases the knob or key on the control box and all circuits of the tuning system are automatically opened, so that no current is wasted. In one embodiment of my invention, the remote control box has only two rotary knobs: one regulates the loudspeaker volume and the other performs the double function of a power switch and rheostat control. When this second knob is in ofi position, the main switch in the receiver is open and the power circuit is disconnected. Instead of having a rotary knob to control the rheostat for tuning in any station on the dial, I may use a set of keys or push buttons representing each a selected station. Each key controls a contact arm adapted to engage the resistance element at such a point that a current of requisite value passes through the switch-controlling coil in the receiver. In other words, when a key is operated, the tuning shaft stops in correct position for the particular station represented by the key. I may also combine 'a set of automatic tuning keys for certain stations with a dialing knob for any station.

The various novelieatures and practical advantages of my remote tuning apparatus will be understood from a description of the accompanying drawings which depict several embodiments of my invention. In these drawings- Fig. 1 represents a side elevation, partly in section, of the tuning mechanism inside the receiver;

Fig. 2 is a plan view on section line 2-2 of Fig. 1;

Figs. 3, 4, and 6 are sectional views on lines 3-3, 4-4, 5-5 and 8$, respectively, of Fig. 1, to show various details of the remotely controlled electromagnetic device associated with the tuning shaft;

Fig. 7 shows a transverse section on line 1-1 of Fig. 2;, Fig. 8 is a section on line 8-8 of Fig. 1; Fig. 9 is an enlarged section on line 3-9 of Fig. 9a is a sectional detail similar to Fig. 9 and showing a modified form of switch contact mounted adjustably'on an insulating disk;

Fig. 10 is an ele v'ational view of one form of remote control box, the cover being partly broken away to show certain parts inside; Fig. 11 shows a plan view of the same box with the outer casing broken away and some parts being sectioned for clearness;

Fig. 12 is'ajc'ross-section on line l2-l2 of Fig. 10

Fig. 13 is a diagram of circuit connections between the remote. control box and the radio recelver;

Fig. 14 shows mote control box;

Fig. 15 is a view similar to Fig. 14, with the cover broken away to revealthe inside mechanism;

Fig. 16 is an enlarged section on line lS-IS of Fig. 15;

Fig. 17 represents, in side elevation; a radio receiver equipped with a modified form of remotely controlled electromagnetic device, the latter being partly sectioned for clearness;

Fig. 18 is a plan view of Fig. 17;

Fig. 19 is a section on line l9-l9 of Fig. 17;

Fig. 20 is a diagram of circuit connections for the remote control box of Figs. 14-16 and the electromagnetic device-of Figs. 17-19;

Fig. 21 illustrates in plan a modified form of switch structure controlled by the electromagnetic device of Figs. 17-19;

Fig. 22 is a section on line 2222 of Fig. 21;

Fig. 23 is a plan view of another form of switch structure controlled by the associated electromagnetic device;

Fig. 24 is a section on line 2 l-2 i of Fig.23;

Fig. 25 is a diagram of circuit connections for glezzlectromagnetic switch mechanism of Figs.

Fig. 26 shows still another form of tuning switch comprising a pair of independently slidable contacts; 7

Fig. 27 is an elevational view of a remote control box having automatic tuning keys in addition to a rotary tuning knob, a portion of the box'being broken away for lack of space;

Fig. 28 is an inside view of the box shown in Fig. 27;

Fig. 29 is an enlarged section on line 29-49 of Fig. 28;

Fig. 30 shows another form of remote control box with automatic tuning keys; and

3 is an inside view of the box shown in Fig. 30.

I shall first describe the mechanism shown in F gs. 1-9. The radio receiver contained in cabinet ID has a tuning shaft I2 which is driven by a small electric motor I 3 mounted on the base plate It of the cabinet. The shaft I2 controls suitable tuning elements which are usually variable condensers arranged in gangs. In Figs. 1 and 2 the tuning elements are diagrammatically indicated at I5, and no further description thereof is necessary. It will be understood that when I refer to shaft I 2 as a tuning shaft, I do not necessarily mean that it carries all or any of the tuning elements, for these may be mounted on a separate shaft operatively connected to shaft [2. I call this the tuning shaft to indicate that its operation controls the variable tuning elements of the receiver, irrespective of where or how they are mounted. The motor shaft l5 carries a worm or spiral pinion ll arranged in mesh with a. gear wheel 88 fixed on one end of a rotary shaft i9,

which is supported me bearing 20 on top of a stand 2i secured to base M. A second stand 22 has a bearing 23 for supporting a rotary shaft 23 in axial alignment with shaft is. A bevel pinion 25 fixed on one end of shaft 26 engages a bevel pinion 26 on the tuning shaft l2, one end of which is journalled in a horizontal bearing 28 on a post or stand 27!.

Referring to Fig. 7, there is a clutch member 29 fixed on one end of shaft 89 anda slidable in elevation another form of reclutch ring 30 is keyed on one end of shaft 24.

A lateral projection 3| on stand 22 carries a pin 32 on which a bellcrank 33 is pivoted. The upper arm of bellcrank 33 terminates in a yoke 34 adapted to engage. in a. circumferential groove 35 of clutch ring 30. A contracting coil spring 36 normally holds the bellcrank 33 in such position that the clutch ring 30 is out of engagement with clutch member 29, so that the motor i3 is disconnected from the tuning shaft l2. When the bellcrank 33 is rocked counterclockwise (as I crank 33 is actuated by a solenoid comprising a,

coil 31 and a reciprocable magnetic core 38, which is connected to one end of bellcrank 33 by a pivoted link 39. When coil 31 is energized, the clutch ring 30 is moved to coupling position, and when the coil is de-energized, the tensionedspring 36 instantly moves the clutch ring to normal inoperative position. The transmission ratio between motor i3 and tuning shaft I2 is so calculated that the shaft is driven at the requisite low speed. In the present instance, the shaft it rotates always in the same direction. If the receiver has condensers that operate only through an arc of 180 degrees and require reversal of movement when minimum and maximum capacity is reached, it is only necessary tointerpose a suitable automatic reversing mechanism R. between the motor-driven shaft l9 or 24 and the tuning shaft l2, as diagrammatically indicated in Fig.

21. It will be understood that the reversing mechanism It is applicable to any one of the various modifications shown in the drawings. This automatic reversal of the tuning shaft at each end of the dial may be effected either by reversing the rotation of the motor shaft through a reversing switch, or 'by interposing mechanical reversing connections. Examples of both forms of reversing connections for tuning shafts are set forth in certain of my copending applications,

' such as Serial Number 338,391.

firm pressure contact with the metal ring 42 on I disk fill. A contact 35 is fixed in disk near its periphery so as to project slightly beyond the face of the disk, as indicated in Fig. 9. A suitable conductor 3? connects the contact 56 electrically with ring 32. This conductor may be an ordinary flexible wire, or it may be a. stiff metal strip soldered at its ends to the contact members 32 and 36. The correct angular position of con tact 66 is determined by adiu'sting the insulating it of disk lil in tight frictional engagement.

. form 59 by screws I4 or otherwise.

7 2,010,904 3 which holds the clip against movement out of adjusted position.

The base plate 14 of the radio cabinet carries a non-magnetic frame indicated as a whole by 48,

which supports a U-shaped permanent magnet 49. The frame 49 has a platform 58 on which the ends of the magnet rest. A strap hinged at 52 surrounds the magnet and is held tight by a bolt 53 hinged at 54 to the platform 58. The strap 5| terminates in a lateral extension 55 provided with a slot 56 for receiving the bolt 53. By tightening the wing-nut 51, the strap 5| is tensioned to hold the magnet 49 rigidly in place. Any other practical supporting means for magnet 49 may be used. The pole pieces 58 of the magnet are shaped to provide a cylindrical space in which a pivoted coil 59 is operatively supported. A cylindrical core 66 of soft iron is preferably inserted in the air space between the pole pieces to concentrate the magnetic flux through the coil. pole pieces 58 and magnetic core 66 form an angular airgap 9| in which the side turns of coil 59 are .free to swing in either direction. \The core 69 is supported in any practical way, as by means of a non-magnetic plate 62 attached to the top of pole pieces 58 by screws 63. The plate 62 is provided with a rib 64 adapted to enter an axial slot or groove 68 in core 69. The connection between rib 64 and slot 60' is sufficiently firm to hold the core securely in concentric relation to the polar faces of the magnet.

The coil 59 is wound on a rectangular non-magnetic frame 65, which may be formed of aluminum or insulating material like stiff moisture-proof paper, fiber and others. The frame 65 carries a pair of axially aligned shafts 66 and 61, which are recessed at their outer ends for receiving pointed pins or set-screws 68 and 69, respectively. The adjustable set-screw 68 is mounted on an upright extension 18 of framework 48 and the pointed pin 69 is carried by an insulated U-shaped bracket II also mounted on the frame. This is clearly shown in Fig. 1. The coil frame 65 is connected .at opposte ends to a pair of spiral springs I2.

The fixed ends of these springs are connected to insulating blocks 13, which are secured to plat- The spiral springs 12 are oppositely arranged and so ad justed as to hold the co l 59 normally in the position shown in Fig. 4. It is convenient to use the insulated springs 12 as conductors for leading the current through the coil, and the ends of the coil are therefore connected to the springs, as diagrammatically indicated in Fig. 13. The shaft 61 of coil frame 65 carries an extension 15, which terminates in a gear sector or arcuate rack bar 15 arranged to mesh with a pinion 'I'I rotatably mounted between two aligned bearing pins 18 and 19 on bracket II. The pn I9 may be in the form of an adjustable set-screw. The hub 80 of pinion ll carries a contact arm 8| arranged. to engage the insulated contact 46 on disk 48. s

The transmission ratio between coil shaft 66-431 and contact arm 8| is 2:1, 50 that the arm rotates through approximately half a revolution when the coil 59 swings through an arc of90 do grees. In Fig. 4 the maximum movement of coil 59 is from normal position to the right-angled position indicated by the dotted outline 59', and it is assumed that the 180 degree are of travel of contact arm 8| takes in the entire broadcasting scale. If the coil 59 is mounted to swing through half a revolution, the multiplying gear connection a 16-11- is not necessary. As seen in Fig. 1, the

pivot axis of the rotary contact arm BI is substantially in axial alignment with tuning shaft l2, whereby th rotary contact members 46 and 8| move abou a common center. The arm 8| is preferably of spring metal adapted to press firmly against contact 46. It is clear that the independently movable contacts 46 and 8| constitute a switch adapted to be closed when they reach the same angular position, which is predeterm ned from the remote control box, as will be explained in due course. The rotary contact 46 need not be mounted directly on shaft l2, for it is sufficient to have the contact move in unison with the shaft, no matter how the contact may be supported. The angular position of arm 8| depends upon the strength of current passing through coil 59, and the strength of the energizing current is regulated in accordance with the station to be tuned in. This current regulation is effected by means of a remote control box which I shall now describe.

Referring to Figs. 10, 11 and 12, there is a small flat box indicated as a whole by 82 which comprises an insulating base 83 and a removable cover 84. The box 82 contains a rheostat comprising a resistance 85 and a rotary contact arm 86. The resistance element 85 may be a coil of fine wire wound closely on a circular insulat'ng strip 81, and a simple way to hold this coil in position is to set it into a semi-circular slot 88 in an insulatingblock or disk 89 on base 83. The wire-wound strip 81 may fit so tightly into slot 88 that no additional fastening means is required. The insulating disk 89 carries a binding post 96 to which one end of resistance coil 85 is connected. In place of a wire resistance, Imay'use a resistance composed of graphite or other composition having comparatively high electrical resistance suitable for the purpose of this invention. The contact arm 86 is fixed on a rotary shaft 9| which carries on its outer end a knob or other suitable finger piece 92, preferably of insulating material. The inner end of shaft 9| extends into a recess 93 in block 89, and a conducting spring strip 94 secured in the recess is connected to the projecting end of shaft 9| by a cross-pin 95 or otherwise. The shaft is therefore always in good electrical contact with conductor 94. A binding post 96 on theinsulating block 89 is electrically connected with strip 94, so that therheostat arm 86 is connected in circuit by merely attaching a conductor to the binding post. I

The rheostat arm 86 is normally held out of contact with resistance 85 by the spring blade 94,

when the arm 86 encounters the stop 98 at the other end of its movement, the amount of resistance in the coil circuit is a minimum. The rheostat shaft 9| carries an indicator plate or disk 99 provided with'a scale I 06 on which the broadcasting stations are suitably indicated. It

is customary to divide these scales into one hundred equal divisions, and I have followed this practice in Fig. 10 where the scale is in zero posltlon. A window III in the top of box 82 permits reading of the indications on disk 99. To

. facilitate the tuning in of the stations used most frequently, the dial plate 99 may have those stations identified by their call letters.

Most radio receivers of the present day are opelectric power is turnedo'n and off by a main switch. The remote control box 82 of Figs. 10,

1'1 and 12 is also provided-with a suitable power switch I02 operated bya toggle lever I03 or otherwise. It will not be necessary to show or describe the structural details of switch I02, because such switches are well known and obtainable in the open market. The volume of loudspeaker reproduction is regulated from the remote control box by simply turning a knob I04 which operates a conducting strip H0. Two fixed stops II 2 and H3 on disk I01 limit the movements of rheostat arm I05, which is carried byfiarotary shaft II4 operated by knob I04.'

Fig. 13 indicates diagrammatically the operative connections between the radio receiver and 'the remote control box 02. A plug II5 adapted to be inserted in an ordinary house-lighting socket has a pair of leads H6 and III which may be connected to a suitable voltage-reducing device I I8. The service main I I1 includes a switch comprising a movable arm H9 and a stationary contact I20. The arm II9 may be a spring blade which normally tendsto remain in open position. The normally open switch I I S-I20 is shunted by a hand-operable switch comprising a movable contact member I2I and a fixed contact I22, which constitute the main power switch of the receiver. Two branch conductors I23 and I24 lead into the radio cabinet where they are i properly connected in the system of the receiver, as-will be understood without explanation. The switch arm H9 is controlled by an electromagnetic relay indicated as a whole by I25 and comprising a magnetic field frame I26, a magnetizing coil I21 and a movable armature I28 pivoted to the field frame at I29. The armature I28 is normally held by a contracting coil spring I30 against a fixedstop I3I away from thefield frame by a wire I34 to a switch terminal I35 in the remote control box 82. The other switch terminal I36 is connected by a wire I31 to the service main I I6. The switch terminals I35-I36 are adapted to be electrically connected by a hand-opera ble plug I38. It may be assumed that the switch parts I35,.I 36 and I33 in Fig. 13 are a diagrammatic representation of the main switch I02 in the remote control box.

Two conductors I39 and I40 lead from the voltage-reducingdevice H8. A wire III connects one side of motor I3 to conductor I39, and the other side of the motor is connected to one end of clutch coil 31 by a wire I62. The other end of coil 31 is connected by a wire I43 to a stationary switch contact III, which is normally engaged by a movable contact arm I45. A wire I 36 connects the switch arm I635 with a stationary contact I41. A movable contact I48 associated with contact III is connected to conductor I 33. The movable switch arms I45 and I46 maybe in the knob I04 is turned.

erated from, the house-lighting circuit, and the the form of spring blades so mounted and tensioned that the arm I45 normally engage'sits contact I44, while the other arm I48 is normally out of engagement with the adjacent contact I41. It will be seen that the normally closed switch I 44I45 and the normally open switch I4I-I48 are connected in series in the circuit of the electric motor I3 and clutch coil 31, so that both switches must be closed to energize the motor and connect the driving shaft 24 with the motor-driven =shaft I9. i

The normally closed switch arm 5' is controlled by an'electromagnet comprising a coil- I49 and a magnetic core I50. Similarly, the nor-- mally open switch arm I48 is controlled by a coil I5I wound on a magnetic core I52. When coil I49 is energized, the arm I45 is attracted and disengages contact I44 to open the circuit of motor I3 and coil 3I. When 'coil I5I is energized, the arm I48 is moved into engagement with contact I4! to close the circuit of motor I3 and clutch coil 31, assuming theswitch I44-I45 to be closed. One side of coil I49 is connected by a wire I53'to conductor I 39, and the other side of the coil is connected by a wire I54 to the rotary'contact arm 8!. One side of coil I5I is connected to conductor I39 and the other side of the coil is connected by a wire I55 to one of the conducting springs 12 of coil 5'). The other conducting spring 12 is connected by a wire I56 to one end of the rheostat resistance 85 inthe remote control box 82. The rheostat arm 06 is connected by a wire I51 to conductor I40. The contact fin get 44 which engages the conducting ring 42 on shaft I2 is connected to conductor I40 by a wire I58. One end of the volume-regulating resistance I06 in the remote control box is connected to a conductor I59, and the associated contact arm I05 is connected to a conductor I60. The two conductors I59 and I60 are connected in any practical way to cause a variation in the loudspeaker volume by the control of resistance I06. By way of example, I might suggest that the rheostat I 05I06 could be connected across the secondarycoil in the first audio frequency stage. It is immaterial through what connections the volume of reproduction is controlled when In actual practice, the two together with their associated switches may be mounted on a single supporting panel or bracket I6I secured; to the base plate l4 of the radio cabinet, as shown in Figs. 1 and 2. The spring arms I45 and I46 are mounted on lateral projections or ears I62,and the stationary contacts I44 and I41 are supported on lateral projections I63. The two pairs of projections I62 and I63 may convenientlybe formed integral with panel I6I, which may be of sheet metal or insulating material. If the panel is made of metal, the supported switch contacts must be properly insulated. The panel IGI may also carry an arm I64, to which one end of spring 36 is attached.

eons I49 and I5I In using the remote control box, the operator A: he turns the knob 92 until the identifyingiii dicia of that st htion appear in the window IIII. we may assume that, when the rheostat arm 86 is in the position indicated in Fig. 13, theindicator of the control box points to station A. No circuits are closed by the mere rotation of arm 86, because the latter is normally out of contact with resistance 85. After the operator has adjusted the tuning knob 92, he pushes it in and closes the circuit through coils 59 and .I5 I as follows: starting with conductor I89, we go through coils I5I and 59 in series, through cable wire I 56, resistance 85, contact arm 86 and through wire I51 to the one way or the other.

return conductor I148. The energized coil I5I instantly closes the switch arm I48 so that the circuit is closed through the windings or motor I8 and coil 31 as follows: starting with conductor I39, we go through motor I3 and coil 31 in series, wire I48, normally closed switch contacts I44- I45, wire I46, switch contacts I41--I48 which are now closed by the action of coil I5I, and to the return conductor I40.

The energizing of motor and coil 81 connects the tuning shaft I2 with the driving shaft, I

andthe disk 40 is now slowly rotated. The energizing of coil 59 causes the same to swing in the magnetic field until the electromagnetic action of the coil is counterbalanced by the two tensioned springs 12. The contact arm 8| therefore stops in a position depending on the current strength in coil 59. We may assume that for station A the switch am. 8I stops in the position indicated in Fig. 13. The tuning shaft I2 carries the contact 46 around with it until the contact encounters the arm 8|, whereupon the coil I49 is energized through the following connections: conductors I89 and I58, coil I49, wire I54, arm 4 8|, contact 46, collector ring 42, brush 44, and through wire I58 to the return conductor; I49. The energizing of coil I49 opens the switch arm I and breaks the circuit of motor I3 and clutch coil 81. Therefore, the moment when the independently movable switchmembers 46 and M meet, the tuning shaft stops and remains in tuning position for the selected station.

The above operation takes PM for any position of rheostat arm 86 in the remote control box 82. The resistance 85, coil and springs 12 are so calibrated that theswitch arm 8Iactuated by coil 59 stops in correct timing position for the station represented by the position 01 arni 86. This calibration lies within the skill of the electrical expert. The voluin'e of reproduc-' 1 tion is regulated by merely turning the knob I94 As soon as the operator hears the selected station, he releases the knob or button 92, whereupon the circuits of coils 81, 69, I49 and I5l are automatically opened, so that no current is wasted. The only coil that remains I energized as long as the switch contacts I85-I86 remainclosed, is the relay coil I 21, but that consumes a negligible amount of current. If the rotating contact 46 should meet the contact. arm 8| before the latter has come to rest-position, the motor and clutch circuits will be momentarily interrupted, but the arm 8| will continue to move until it reaches its predetermined position. As soon as the two contacts are separated,.the motor I8 and clutch coil 81 are again energized and the tuning shaft I2 continues to rotate until the contact 45 meets the adjusted arm 8|. Thereupon the tuning shaft stops for good in preselected position until the next station is tuned in. Attention is called to the fact that onlysix wires of low voltage are contained in the electric cable connecting the remote control box with the radio receiver. These six wires cross the imaginary line I in Fig. 13, which has been dravfi merely to indicate visually that all wires crossing that line are housed in the connecting cable. Since all wires in the cable are of low voltage, no arcing in the remote control box is possible, and all danger due to high voltage is eliminated.

Figs. 14, 15 and 16 show a modified form of remote ccntrol box in which the rheostat arm also controls the main power switch, so that the separate finger piece I03 of Figs. 10 and 11 is eliminated. To avoid needless repetition of description, all parts common to Figs. 10-12 and 14-16 is mounted at one end on the insulating base 89 and normally tends to engage. the fixed contact I68. The tuning knob 92 carriesa pointer I69 arranged to move over the scale I 18on top of the box. When the pointer I 69 is in 011 position, the rheostat arm 86 inside the box rests against the stop 91 and holds the spring finger I61 open. When the rheostat arm 86 is moved over the resistance 85, the released spring finger I61 automatically moves to closed position and completes the circuit through relay coil I 21. In other words, the switch I61I68 of Fig. 15 takes the place of the separately operated switch I02 in' Figs. 10 and 11 and is connected to relay I25 in the same way as contacts 'I35I36 in Fig. 13.

I61I68 open when the pointer I69 is in oil! position. The electrical connections ofthe various parts in the control box of Figs. 14, 15 and 16 are the same as those shown in Fig. 13.

Instead of setting the adjustable tuning contact 8I by means of the pivoted armature coil 59, I may use a solenoid having a'movable magnetic plunger to which the contact is connected. This modified construction is illustrated in Figs. 17, 18 and 19. It will be noticed that Figs. 17 and 18 differ from Figs. 1 and 2 in that the rotary coil mechanism for settingthe contact BI is replaced by a solenoid device with a reciprocable' plunger. Therefore, since the rest of Figs. 17' and 18 is substantially identical with Figs. 1 and 2, I need not repeat the detailed description of the parts common to those four figures. These common parts are indicated by like reference characters, and I shall therefore describe only the solenoid mechanism in Figs. 1'7 and 18.

A non-magnetic framework I" mounted on base I4 carries a coil I12, which is held in place by a strap I13 or otherwise. The coil I12 has a magnetic plunger I14 mounted for axial movement. A non-magnetic rod I15 is attached to one end of plunger I14 and connected to a cross- ,normal position, the rack bar I18 rigidly to the rod; IA second cross-piece m is connected to the outer end of plunger I14 by a nut I88 or otherwise, and the upper ends of the two cross pieces are connected to a rack bar I86 v arranged in mesh with a pinion I82. A U-shaped bracket I83 fixed on the supporting frame I'II has apair of adjustable screw bearings I84, be-

tween which the pinion I82 is supported for rotary movement in either direction. The hub or shaft I85 of pinion I82. carries a contact arm I88, which corresponds to the arm 8I operated'by the pivoted coil 59 of Figs. 1-3. A light coil spring I81 of good conducting metal may be used to connect the arm I86 in circuit during its movements. Oneend of spring I81 is attached to shaft I85 and the other end of the spring is connected to an insulating block I81 on bracket I83. The spring I81 is not a restoring spring but is used merely as a flexible conductor that may be replaced by any bther suitable connection, It is understood that the rotary contact arm I86 is properly insulated. If the supporting frame!" is of metal and insulated as a whole, no separate insulationis needed for arm I88.

Referring to Fig. 19, a contracting coil spring I88 is connected at one end to the supporting frame "I and at the other end to a nut I89 on screw rod I11. The cross-piece I16 forms a stop for the movement of plunger I14 under the action of coil spring I88. When the plunger I14 is in I8I holds the insulated contact arm I86 at one end of its arc of travel. That is to say, the normal position of arm I88 corresponds to the zero position of the indicator dial on the remote control box. When a the solenoid coil I12 is energized, the magnetic core I14 is drawn in until the electromagnetic action of the coil is counterbalanced by the opposing tension of spring I88. As the plunger I14 is drawn into the coil, the rack bar I8I' rotates the contact arm I88 counterclockwise (as viewed in 19) and the position of this arm depends upon the strength of current passing through coil I12.

Fig. illustrates diatically the circuit f connections between the control box of Figs. '14- 16 and the radio receiver provided with the solenoid mechanism. of Figs. 17-19. It will not be necessary to describe Fig. 20 in detail, because everything that was said in connection with Fig. 13 applies to the other figure. ence between the systems in these two figures is thatthepivoted coil 59 of Fig. 13 is replaced by the solenoid 212-414, and the relay switch I81-I88 in Fig. 20 takes the place of the handswitch II36 in Fig. 13. spending parts in Figs. 13 and. 20 are indicated by the same reference characters, so that the circuits previously traced in Fig. 13 can also be traced in Fig. 20 without the need of repetition.

- When the pointer I89 of Fig. 14 is moved to the desired position on scale I18, the associated rheostat arm 88 allows the switch member I81to close the circuit of relay coil I21 whereby the main power switch II9 of the radio receiver is closed. 'When'the knob 92 is then pushed in to move the contact arm 88 into engagement with resistance 85, a current of predetermined strength passes through coils I5I and I12 in series, and the plunger I14 moves the contact arm I88 to a certain position representing the station to be tuned in. At the same time, the

energized coil I5I closes the switch member I48, whereby the timing shaft is operatively connected with electric motor I3, as previously explained in The only diifer- Similar or corre connectionwith Fig. 13. When the rotating contact 46 encounters the adjusted arm I86, coil I49 is energized and opens the circuit of clutch coil 31 and motor I3. The shaft I2 therefore stops instantly in preselected tuning position.

It is not necessary that coil I5I be connected in series with coil 59 of Fig. 13 or with solenoid coil I12 of Fig. 20, for any other suitable connections may be employed for simultaneously energizing those coils. If the coil I5I is connected in series with coil 59 or I12, the current passing through coil I5I will naturally vary in strength, but the electromagnet I5I| 52 and the associated movable arm I48 are so constructed that the weakest current passing throughcoil I5I is suificient to move the switch member I48 1 to closing position. It goes without saying that the remote control box 'of Figs. 10, 11 and. 12 may be used with the solenoid mechanism of Figs, 18,

19 and 20, and the remote control box of Figs. 14,15 and 16 may be used with the pivoted coil mechanism of Figs. 1-7. In other words, the remote control box of Fig. 13 may be substituted in Fig. 28, and vice versa.

In the construction previously described, the i tuning switches 48-4 of Fig. 13 and 48-I86 of Fig. 20 comprise two contacts mounted for independent movement,,' one contact being movable with the tuning shaft I2 andthe other contact being controlled by the tuning coil 59 or I12. It is possible to mount both contacts on the .same support. A construction like that is shown in Figs. 21 and 22, where the insulating disk 49 on tuning'shaft I2 carries a pair of switch arms I98 and I9I. These arms may conveniently be in the form of flat spring blades mounted atone end on an insulating block I92 and arranged to be normally open at their free ends. -The block' I92 is carried by a U-shaped clamp I93 adapted to be secured to the edge of disk 48 by a set-screw I94 or otherwise. justable, so that the hump or ofiset I95 on switch arm I98 may be arranged in correct radial position on tuning shaft I2 The switch arm I99 is actuated by a rotary cam disk I96 having a projection I91 which is arranged to engage the hump I95 and force the arm I98 against the associated contact I9I to closethe switch.

The cam disk I98 may be operated either by the pivoted coil 59 or the solenoid coil I12. If the armature coil 59 is used, it is only necessary to replace the arm 8I with cam disk I96. in Fig. 21, I have shown the cam' disk I96 mounted on the shaft I85 of pinion I82, which is part of the solenoid mechanism previously-described in connection with Figs. 1'1, 18 and 19. The switch members I99 and I9I are electrically connected by conductors I98 to a pair of insulated collector rings I99 and 290 mounted on the hub of .disk 40. These collector rings are engaged by a pair of insulated brushes or contact fingers '28I and 202, whichmay be mounted on the bearing sleeve 28 or tuning shaft I2. The switch members I9Iland I9I are connected to conductors I54 and I58 in Figs. 13 and 20. The radial position of cam pro- -jection I91 depends'upon the strength of the The clamp I93 is radially adcontact 204.

.connected to'collector rings I99 and 200 mounted The normally open switch 190191 may be replaced by a normally closed switch adapted to be opened when it encounters the tuning projection 191 on disk 196. A construction like this is illustrated in Figs. 23, 24 and 25, where the in-' sulating disk 40 of tuning shaft 12 carries a movable switch arm 203 normally engaging a fixed These two switch members are on the hub 'of disk 40. The switch arm 203 is mounted at one end on a block 205 attached to one face of disk 40. When the projection 191 on disk 196 strikes the hump or offset 206 on switch arm 203, the latter is moved away from contact 204 to open the circuit of motor 13 and clutch coil 31. This will be clear from the circuit diagram of Fig. 25 in which the coil 151 controls a movable switch arm 201. A wire 208 connects the switch arm 201. with contact 204 on disk 40, and-a wire" v to a predetermined radial position that represents the selected station. The closing of switch arm 201 energizes the electric motor 13 and the clutch coil 21, so that the switch arm 203 on disk 40 rotates around the disk 196. When the hump 206 of switch arm 203 encounters the radially adjusted projection 191. the arm 'is thrown open and the circuit of motor 13- and clutch coil 31 is broken. This occurs when the shaft 12 is in tuning position for the station selected by the operator from the remote control box. Otherwise, what has been said about the operation of the systems shown in Figs. 13 and 20 applies to the system of Fig. 25) The tuning projection 191 in Figs. 23, 24 and 25 may also be actuated by electromagnetic mechanism having a pivoted armature coil like the coil 59 in Figs. 16. It will be undersood that the normally closed switch 203-204 may be mounted on disk 196, and the projection 191 will then be carried by disk 40 or otherwise connected to the tuning shaft 12. The modification of Figs. 23, 24 and 25 has the practical advantage that it dispenses with coil 149 and switch 144-145 in Figs. 13 and 20.

Fig. 26 shows a tuning switch comprising a pair of independently movable contacts 211 and 2 2 mounted for rectilinear movement and suitably insulated. The contact 211 is carried by a rack bar 213 supported for slidable movement in framework 111. A pinion 214' fixed on a rotary shaft 214' meshes with rack bar 213 and thereby moves the insulated contact 211 in one direction or the other. The shaft 214' rotates in alternately opposite directions inunison with the adjustable tuning elements of the receiver. It is immaterial how the shaft 214' is connected with I the electric motor 13, provided the rotation of the shaft is automatically reversed when the contact 211 reaches either end of its line of travel.

The contact 212 is mounted on a rod 215 which is atached to the cross pieces I16 and 119 of the solenoid core 114. Otherwise, the solenoid structure of Fig. 26 is the same as thatshown in Fig. 19. When the coil 112 is energized by a current of predetermined strength, the magnetic core 1.14

station. The shaft 214 continues to rotate until the contact 211 engages the previously adjusted contact 212, whereupon the motor circuit is interrupied and the tuning shaft 12 stops. It will not be necessary to show any circuit connections for the device of Fig. 26, because the reciprocating contacts 211 and 212 are connected in thesame way as contacts 46 and 81 in Fig. 13

and contacts 45 and 186 in Fig. 20. In other words, contact 215 is connected to conductor 158 and contact 212 is connected to conductor 154. In the remote control boxes of Figs. -12 and Figs. 14-16, the tuning knob 92 moves the rheostat arm 86 to bring in any station within range of. the dial. This means that when a person wants a particular station, he has to watch the indicator for the call letters or other identifying notations of the desired station. In every location throughout the United States, it is possible to obtain almost all desirable broadcast programs from a few stations. For this reason I prefer to provide the remote control box with a few automatic tuning keys or buttons in addition to (or in lieu of) the dialing knob 92.

Figs. 27, 28 and 29 show a remote control box having a set of automatic tuning keys or push buttons 211 which are supposed to represent certain stations A-E. By way of example I have shown five buttons, but any other number. may be used. buttons. 211 are mounted on the ends of switch arms 218, which project through a narrow semi-circular slot 2 I 9 in the cover of the box. The arms 210 may conveniently be shaped from fiatv spring metal and are mountedon a semicircular conductor bar or rail 220 which is fastened' by screws 22: to the insulating base 222 of the box. The supporting bar 220 may be stamped from a single piece of sheet brass. The spring arms 218 may be adjustably mounted on the curved rail 220, and a simple way of doing this is by means of clamping fingers 223 and 220 formed integral with the arms. The fingers 224 are formed by cutting a slot 225 near the base of each arm 218. The contact rail 220 may be formed with a narrow section or neck 225 which the spring fingers 223 and 224 grip on opposite sides, as clearly shown in Fig. 29. The arms 213 are firmly held by friction in any radially adjusted position, and yet it is easy to change any arm to another position for a different station. If the arms 218 are not intended to be radially adjusted, the arcuate slot 219 is not necessary. The buttons or keys 211 are separable from arms 218 to permit removal of the cover, if that should be necessary.

Still referring to Figs. 28 and 29, the insulating base 222 carries a circular strip of resistance material 221, which may be a graphite mixture or a coil of closely wound resistance wire. The rheostat arms 218 are normally held by inherent tension out of engagement with resistance element 221. When the operator wants to tune in any one of the stations A-E, he merely presses the button that repre.ents the desired station, whereupon the same operations take place as .'previously described in connection with the circuit diagrams of Figs. 13, 20 and 25. In addition to the automatic tuning buttons 211, I may also use the dialing knob 92 which moves the rheostat arm 86 over the resistance 221 for any station that may be broadcasting.

In the modification of Figs. 30 and 31, the tuning buttons 22a representing stations F-K operate rheostat arms 229 which are mounted on a straight conducting rail or bar 230. The free ends of arms 229fmake contact with a resistance element 22I when the keys or buttons 228 are pushed in. The iresistance member 23 I, may be a coil of closely wound wire or a strip of resistance material like graphite. The outer ends of arms 229 project through a straight slot 232 in the top of the box. It may be assumed that the individual rheostat arms 229 are 'adjustably mounted on bar,230 in the same manner as the radially arranged arms H8 in Figs. 28 and 29. If the arms 229 are not intended for adjustment along the supporting bar 230, the slot 232 isnot necessary. The remote control boxes of Figs. 27-31 are also provided with an on-oif switch and a volume control knob, as previously explained in connecscope of the appended claims. Also, some features of the invention may be used without others, so that all of them need not be embodied in a single apparatus or system. 1

I claim as my invention:

1. In electric control apparatus, thecombination of a shaft, an electric motor for operating said shaft, a member movable with said shaft, a second member movable independently of said shaft to a plurality of positions, a normally closed electric switch carried by one of said members, means on the other member for opening said switch and stopping said motor when saidtwo members reach predetermined relative positions, an electromagnetic device for controlling the position of said second member in accordance with the strength of current which energizes said device, and manually operable means for regulating the strength of said energizing current to predetermine the final position of the second member.

*2. The combination of an adjustable shaft, a movable member associated with said shaft, electric mechanism'for simultaneously operating said shaft and member, an electromagnetic device including a coil, a second member disconnected fromsaid mechanism and operable by said device to a position depending upon the strength of current in said coil. a switch controlled conjointly by the relative positions of saidmembers to stop said mechanism, a resistance in circuit with said coil, and a set of key-operated contact arms for varying said resistance to regulate the current through said coil, each of said arms representing a selected position of said second member.

3. Apparatus comprising an adjustable a movable member'associated with said shaft,

electric mechanism for simultaneously operating said shaft and member, 'an electromagnetic device including a coil, a second member disconnectedfrom said mechanism and operable by said device to a position depending upon the strength of.current in said coil, a switch controlled conjointly by the relative positions of said members to stop said m, a rheostat for regulating the {current through said coil, said rheostat including a manually adjustable contact apropos alternately opposite directions through a definite path oftravel, means for operating said member at substantially constant speed, a second member movable independently of said first member, an electromagnetic device for operating said second member in accordance with the strength of current which energizes said device, the speed and direction of movement of said first member being independent of the operation of said device, means for regulatingthe strength of said energizing current to predetermine the position of said secondmember and means controlled by the position of said second member for stopping said first member.

5. The combination of a shaft adapted to occupy any one of a plurality of predetermined positions, an electric motor for operating said shaft, a member movable with said shaft, a second member movable independently of said shaft and I arranged to engage said first member, electromagnetic mechanism for operating the second member to predetermined position, the extent of movement of the second member depending upon the strength of current that energizes said mechanism, "a manually controlled rhe'ostat for regulating the strength of said energizing current to predetermine the position of the second member, and switch connections for automatically opening the motor circuit when said members engage.

s. The combination of a rotary shaft, means for operating said shaft through a definite arc in opposite directions, an electromagnetic device for controlling said shaft-operating means in accordance with the strength of current energizing said device, so that the strength of said energizing current determines the position in which said shaft stops, a rheostat for regulating the strength of said energizing current, a rotary finger piece adjustable in opposite directions for controlling said rheostat, the direction of rotation of said shaft being independent of the direction of movement of said finger piece, and an indicator associated with said finger piece to indicate the preselected stopping position of said '7. The combination of a shaft adapted to rotate through a definite arc in alternately. opposite directions, an electric motor for operating said shaft, a member movable with said shaft, :5. second member movable independently of said shaft, .electro-magnetic mechanism for operating the second member to predetermined position, the extent of movement of the second member depending upon the strength of current that energizes-said mechanism, a finger piece selectively movable in opposite directions to any desired position, means controlled by said finger piece for regulating the strength of said energizing current to predetermine the position of the second member, the direction of rotation of said shaft being independent of the direction of movement of said finger piece, and means for automatically stopping said motor when said independently movable members occupy certain positions in relation to each other.

8. A remote control box having a set of individually operable push'buttons and a rheostat controlled by said buttons, the operation of each circuit of said coil,,so that the operation of each vary the operative positions of said part in acpush button causes'said coil to move said mem- J cordance with the position of each member, and

ber to a predetermined position.

9. A remote control box having a set of individually operable push buttons, a rheostat controlled by saidbuttons, the operation of each button including a certain ohmic value of said rheostat in circuit, in combination with a coil adapted to be energized by an electric current controlled by said rheostat, a movable member operable to a plurality of different positions depending upon the strength of current in the circult of said coil, so that the operation of each said element .and normally out of engagement therewith, said members being separately operable to include different ohmic values of said resistance element in the energizing circuit of said device, means whereby the position of said adjustable part depends upon the strength of current in said energizing circuit, each of said members representing a certain position of said movable part, so that the operation of any contact member causes said electromagnetic device to. move said part to a preselected position, and

mechanism controlled by the final position of said part.

11. The combination of an insulated resistance element, a conducting bar adjacent said element, a-plurality of spring contacts mounted on said bar in predetermined spaced relation and normally out of engagement with said resistance element, a plurality of keys or push buttons connected to said contacts for individually oper-r; ating the latter, each contact when operated including a certain ohmic value of said resistance element in circuit, a rotary shaft adapted to occupy a plurality of different positions, means for operating said shaft, and electromagnetic mechanism for controlling said shaft-operating means, said mechanism being controlled by an electric circuit including said variable resistance element, whereby the position of said shaft is predetermined by the operation of a particular key.

12. The combination of an .electromagnetic device, a movable part adapted to be actuated by said device to a plurality of predetermined positions, a resistance element adapted to be included in the energizing circuit of said device, a'

set of spaced contact members associated with said element and normally out of engagement. therewith, said members being separately operable to include different ohmic values of said resistance element in the energizing circuit of said device, means whereby the position of said ad iustable part depends upon the strength of current in said energizing circuit, each of said members representing a certain position of said movable part, so that the operation of any contact member causes said electromagnetic device to move said part to a preselected position, a common conducting bar on which said members are mounted so as to be separately adjustable to mechanism controlled by the final position of said part.

13. In apparatus for controlling the angular 5 movement of a shaft, the combination of a rotary shaft, an electric motor for operating said .shaft at substantially constant low speed, a member movable with said shaft, a second member movable independently of said shaft and arranged to engage said first member, an electromagnetic device for actuating the second member to predetermined position, the speed of said motor being unaffected by the speed of operation of said second member, manual means selectively operable, electric means connected with said device and controlled by said manual means to regulate the operation of said device, whereby the position of the second member is predetermined by the selective operation of said manual means, normally open switch mechanism in the electric circuit of said motor, a relay adapted when energized to close said switch mechanism, connections whereby said electromagnetic device and said relay areenergized by the operation of said manual means, whereby the motor circuit is not closed until said manual means is operated, and means whereby the engagement of said members automatically breaks the motor-circuit and stops said shaft in preselected position.

14. In apparatus for controlling the angular movement of a shaft, the combination of a rotary shaft, an electric motor for operating said shaft at substantially constant low speed, a member movable with said shaft, a second member movable independently of said shaft and arranged to engage said first member, a device for actuating the second member to predetermined position, manual means selectively operable for controlling the operation of said device, whereby the position of the second member is predetermined by the selective operation of said manual means, two series switches in the electric circuit of said motor, one of said switches being normally open and the other switch being nor-- 5 mally closed, means for closing said normally open switch by the operation of said manual means, whereby the motor circuit is not closed until said manual means is operated, and means for automatically opening said normally closed 59 switch when said two members engage to break the motor circuit and stop said shaft in preselected position.

15. In apparatus for controlling the angular movement of a shaft, the combination of a rotary shaft, an electric motor for operating said shaft at substantially constant low speed, a member movable with said shaft, a second member movable independently of said shaft and arranged to engage'said first member, an electromagnetic de- 60 vice for actuating the second member to predetermined position, manual means selectively operable, electric means connected with said device and controlled by said manual means to regulate the operation of said device, whereby the position 55.

of the second member is predetermined by the selective operation of said manual means, two series switches in the electric circuit of said motor, one

of said switches being normally open and the other switch being normally closed, a relay adapted when energized to close said normally open switch, connections whereby said electromagnetic device and said relay are energized by the opera tion of said manual means, whereby the motor 2 0 1 1 is not closed until said manual means is bers engage to break the motor circuit and stop said shaft in preselected position.

16. In apparatus for controlling the angular movement of a shaft, the combination of a rotary shaft, an electric motor for operating said shaft at substantially constant low speed, a member movable with said shaft, a second member movable; independently of said shaft and arranged to engage said first member, an electrmagnetic device for actuating the second member to predetermined position, manual means selective y operable, electric means connected with said device and controlled by said manual means to regulate the operation of said device, whereby the position of the second member is predetermined by the selective operation of said manual means, two series switches in the electric circuit of said motor, one of said switches being normally open and the other switch being normally closed, a relay adapted when energized to close said normally open switch, connections whereby said electromagnetic device and said relay are energized by the operation of said manual means, whereby the motor circuit is not closed until said manual means is operated, means for automatically opening said normally closed switch when said two.

members engage to break the motor circuit and stop said shaft in preselected position, and means whereby the operation of said manual means deenergizes said electromagnetic device and said relay.

17. In apparatus for controlling the angular movement of a shaft, the combination of a rotary shaft, an electric motor for operating said shaft at substantially constant low speed, a member 'movable with said shaft, a second member movable independently of said shaft and arranged to engage said first member, an electromagnetic device for actuating the second member to predetermined position, a rheostat having manually operable means for controlling the operation of said device, whereby the position of the second member is predetermined by the selective operation of said rheostat, normally open switch mechanism in the electric circuit of said motor, a relay adapted when energized to close said switch mechanism, connections whereby said electr magnetic device and said relay are energized y the operation of said rheostat, whereby the motor circuit is not closed until said rheostat is operated, and means whereby the engagement of said members automatically breaks the motor circuit and stops said shaft in preselected position, said rheostat constituting a normally open switch in the circuit of said device and said relay.

18. In apparatus for controlling the angular movement of a. shaft, the combination of a rotary v shaft, an electric motor for operating said shaft at substantially constant low speed, a member movable with said shaft, a second inember movable independently of said shaft and arranged to engage said first member, an electromagnetic device for actuating the second member. to prede-' termined position, a normallyopen circuit for said device, arheostat having manually operable means controlling the operation of said device,

.whereby the position of the second member is predetermined by the selective operation of said rheostat, two series switches in the electric circuit of saidmotor, one of said switches being normally open and the other switch being normally closed, a relay adapted when energized to close said normally open switch, connections whereby said electromagnetic device and said relay are energized by the operation of said rheostat, whereby the motor circuit is not closed until said rheostat is operated, means for automatically opening said normally closed switch when said two members engage to break-the motor circuit and stop said shaft in preselected position, and means for automatically die-energizing said electromagnetic device and said relay when the operator releases the manually operable means of said rheostat. r

19. In apparatus for controlling the angular movement of a shaft, the combination of a rotary shaft, an electric motor for operating said shaft at substantially constant low speed, a member movable with said shaft, a second member movable independently of said shaft and arranged-to engage said first member, an electromagnetic device for actuating the second member to predetermined position, manual means selectively operable, electric means connected with said device and controlled by said manual means to regulate the operation of said device, whereby the position of the second member is predetermined by the selective operation of said manual means, two series switches in the electric circuit of said motor, one of said switches being normally open and the other switch being normally closed, a relay adapted when energized to close said normally open switch, connections whereby said electromagnetic device and said relay are energized by the operation of said manual means, whereby the motor circuit is not closed until said manual means is operated, a second relay adapted when energized to open said normally closed switch and thereby break the motor circuit, and

connections for automatically energizing the second relay when said two members engage.

20. In apparatus for controlling the angular movement of a shaft, the combination of a rotary shaft, an electric motor for operating said shaft at substantially constant low speed, a contact movable with said shaft, a second contact movable independently of said shaft and arranged to engage said first contact to close an electric circuit, an electromagnetic device for of said switches being normally open and the other switch being normally closed, a relay adapted when energized to close said normally.open switch, connections whereby said electromagnetic device and said relay are energized by the operation of said manual means, whereby the motor circuit is not closed until said manual means is operated, and a second relay for automatically opening said'normally closed switch when said two contacts engage, whereby the motor circuit isbroken and said shaft is stopped in preselected position.

ADOLPH A. THOMAS. 

